This invention relates to an agricultural harvesting machine and more particularly to a forage harvester having a rotary cylinder type cutterhead that registers with an elongated shear bar at the cutterhead periphery, the cutterhead knives cooperating with the shear bar to reduce crop material being fed over the shear bar into the cutterhead.
A forage harvester of the above general type is disclosed in U.S. Pat. No. 3,677,316, also assigned to the assignee herein. The forage harvester disclosed in said patent includes a rotary cylinder type cutterhead having knives at the cutterhead periphery that register with a transverse shear bar adjacent the cutterhead periphery, the crop material being fed over the shear bar and into the cutterhead. As described in said patent, maintenance of the sharpness of the cutterhead knives has long been an irksome problem associated with the operation of such a forage harvester, the knives needing frequent resharpening during operation of the machine. The reverse rotation of the cutterhead, as described in said patent, has resulted in improved sharpening of the knives, although it is still necessary to sharpen the knives at relatively frequent intervals.
Along with maintaining properly sharpened knives, it has been found necessary for proper operation of such machines, particularly with respect to power consumption, that it is necessary to maintain optimum registry of the shear bar with the cutterhead periphery, a clearance of less than 0.015 inch being desirable. However, since each sharpening of the knives removes material from the knives and reduces the diameter of the cutterhead, for optimum performance it is necessary to readjust the shear bar-cutterhead clearance after each knife sharpening. Typically, the shear bars are clamped to a supporting structure and adjustment of the shear has entailed first loosening the clamping bolts at opposite sides of the cutterhead housing, and then rotating an adjusting cam or bolt to shift the shear bar. Adjusting mechanims of the above general type are disclosed in U.S. Pat. Nos. 3,419,055 and 4,055,309. However, access to the clamping and adjusting bolts at the opposite ends of the shear bar has been a problem, since, in a pull type machine, such as shown in said U.S. Pat. No. 3,677,316, the outboard ground engaging wheel is generally disposed adjacent the outer side of the housing side wall, a header is usually mounted on the front of the cutterhead housing, and, at least in some cases, drives from the cutterhead shaft or drives for the feed rolls are also disposed alongside the housing, with shielding covering both the drives and the ends of the shear bars. In the case of the shear bar adjusting mechanism on the inboard side wall, access is also difficult, since various drives for the forage harvester feed rolls and/or header are typically located adjacent the inboard cutterhead side wall. Moreover, relatively large clamping forces are employed to clamp the shear bar so that relatively large tools are necessary to adjust the shear bar, all of which has made shear bar adjustment so inconvenient that in some cases the operator neglects to adjust the shear bar after sharpening of the cutterhead knives, with the accompanying result of loss in forage harvester efficiency.